The disclosure relates to an arrangement and a method for determining the position of a unit in an electrophotographic printer or copier. The arrangement includes a sensor arrangement which outputs a sensor signal dependent on the position of the unit.
Modern high-performance printers with printing speeds of more than 150 sheets DIN A4 per minute are modularly structured so that a quick replacement of units can be carried out. Further, such a modular structure allows a simple and quick maintenance as well as simple and quick cleaning possibilities of the unit of the electrophotographic printer. In particular, up to five developer stations per printing unit are included in such high-performance printers, common high-performance printers having at least two printing units. For cleaning and maintenance services, individual developer stations can be taken out of the printer or copier as units and/or can be brought into an appropriate cleaning and/or maintenance position for these services.
In order to enable a multi-color-printing, in known high-performance printers several developer stations are allocated to a printing unit and are swung into contact with a photoconductor or will be swung into contact therewith depending on the operating state. These developer stations contain various colors, in particular black, magenta, cyan, yellow and/or customized colors. It must be possible for service technicians to easily replace such developer stations and for an operator to easily clean the same. For cleaning and replacement, first, all developer stations are successively swung away from the photoconductor. Each developer station has at least an own drive unit which serves to mix the toner particles and the toner particle mixture as well as to supply toner material. For removing the developer station from the printer, usually a locking that prevents the developer station from being taken out has to be released.
In a high-performance printer described in the International Patent Application WO 98/39691, for the purpose of cleaning a developer station the mechanical locking of a developer station has to be released in the swung-out printing position by pulling out a locking pin. Subsequently, the developer station is pulled out up to the cleaning position. In the cleaning position the locking pin engages in an aperture provided therefor. As a result, the developer station is in the cleaning position and can be cleaned by the operator. After cleaning, the engaged locking pin has to be released and the developer station has to be pushed in up to the swung-out printing position. In the printing position the locking pin engages in a second aperture provided therefor. The developer station is thus fixed and secured in the printing position. The content of the International Patent Application WO 98/39691 is incorporated by reference into the present application.
When the developer station in the high-performance printer described in WO 98/39691 is to be replaced, then the locking of the developer station in the swung-out printing position has to be released by pulling out the locking pin and the developer station has to be pulled out up to the stop in the same manner as for cleaning the developer station. Subsequently, the total locking of the developer station has to be released and the station has to be lifted out. Thereafter, the new developer station is placed therein and is secured against removal by means of the total locking. Subsequently the developer station is pushed into the printer up to the swung-out printing position in which the locking pin engages in the aperture provided therefor.
When a developer station of a printing unit is to be cleaned or replaced, then first all developer stations have to be swung away from the photoconductor. After the cleaning or the replacement, i.e. when the cleaned or replaced developer station is again in the swung-out printing position, all stations are again successively swung into contact and the printing operation is enabled.
Both a control unit arranged on the developer unit for controlling the sequence of operations of the developer station and the at least one drive arranged on the developer station are only supplied with current and are operational after the developer station has been swung into contact.
When the developer stations are successively swung into contact, it has to be guaranteed that the stations which are swung into contact are locked in the printing position, since otherwise, when the stations are serially swung into contact, collisions between the individual stations might occur. Further, the motors for the swing motions which are provided at mounting locations where no stations are installed must not be actuated or activated. In the prior art, the position of the developer station is merely ensured by the locking pin. When, however, the developer station is not correctly pushed in up to the printing position after cleaning or after replacement, then the motor for the swing motions will nevertheless be activated and tries to swing the incorrectly positioned developer station into contact. This may result in damage to the printer, the developer station to be swung into contact, or to adjacent developer stations.